The present invention relates to buckles to be used in safety belt devices, such as seat belt devices, mounted on seats of automobiles and other transportation vehicles. In particular, the present invention relates to a buckle provided with a buckle switch to be switched by a latching operation of a tongue and the buckle.
Presently, seat belt devices are mounted on seats of automobiles and other transportation vehicles for protecting passengers in a case of emergency, such as collision. The seat belt device of this type is generally provided with a buckle for easily fasten and unfasten a belt. The buckle includes a latch member for latching a tongue, which is resiliently urged in the latching direction toward the tongue, and a lock member for maintaining the latch member and the tongue in a latched state.
The buckle is provided with a buckle switch for determining a latched state. The buckle switch displays the latched state of the tongue and buckle, and in accordance with the latched state of the tongue and buckle, operates and controls other components of the seat belt device, such as a retractor, and automotive devices relating to the operation of the seat belt device.
A buckle switch is known, which generally uses a contact-type switch, such as a board-type switch or a microswitch. In the contact-type switch, switching is repeatedly performed at a contact part of the buckle switch by latching and unlatching the tongue and buckle. Therefore, there is a risk of a poor connection due to wear of the contact part or the like, and the durability is not always on a high level.
A buckle switch using a non-contact type switch is proposed in Japanese Unexamined Patent Publication (KOKAI) No. 10-155521. In the non-contact type buckle switch disclosed in this publication, light emitted to a latch member for latching a tongue by a field supply source of a light-reflection device is applied to a reflecting surface of the latch member, and the light reflected by the reflecting surface is detected by a field-effect unit of the light-reflection device, thereby determining a latched state and an unlatched state of the tongue and buckle.
By using the non-contact type buckle switch, the risk of a poor connection due to wear of the contact part is avoided because the switch does not include contact parts, thereby improving durability.
However, in the non-contact type buckle switch using a light reflection device, a risk of difficulty in reliable operation is anticipated because the light-reflection device is likely to become dull to reflected light due to fixture errors of the latch member and the light-reflection device, foreign materials, such as liquid like water and juice, dust, and rust formed by liquid. The contact-type switch is also likely to be affected by the foreign materials, such as liquid like water and juice, dust, and the rust formed by liquid.
Accordingly, an object of the present invention is to provide a buckle provided with a buckle switch which is improved in durability and can more reliably operate.